Systems, methods, and computer-readable media for modeling complex wellbores in field-scale reservoir simulation

ABSTRACT

Systems, methods, and computer-readable media are provided for a near-well unstructured grid model builder for generating a full-field unstructured grid for reservoir simulation. As described further below, the near-well unstructured grid model builder may include a workflow interface and a parallel unstructured grid model builder. The inputs to the near-well unstructured grid model builder may include existing well trajectory and completion data, future well data, a geological model, a structured grid simulation model, or any combination thereof. The near-well unstructured grid model builder may output a near-well unstructured grid having a specified grid resolution in regions of interest that include a well.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/766,056 filed on Feb. 18, 2013, entitled “Systems Methods, andComputer-Readable Media for Modeling Complex Wellbores in Field-ScaleReservoir Simulation,” the disclosure of which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the computerized simulation ofhydrocarbon reservoirs and, more particularly, to computerizedsimulation multiphase multicomponent flow and transport processesinvolving complex well geometry such as complex maximum reservoirscontact (MRC) wells. These wells can be densely populated within thereservoirs.

2. Description of the Related Art

Oil, gas, and other natural resources are used for numerous energy andmaterial purposes. A reservoir in a geologic body or other formation maycontain oil, natural gas, water, and several constituent compounds.Reservoirs simulation refers to the modeling of such components topredict the multiphase fluid flow and transport processes in thereservoir. Reservoir simulations may be run before, during, or after awell is drilled to determine the viability of the well, the productionrate, and so on. With the advancement of drilling technology, wellshaving multiple branches and highly complex geometries are increasinglybeing deployed in some reservoirs. In order to enhance production andother processes in these reservoirs, the accuracy of flow modeling andother techniques has presented numerous challenges and increaseddifficulty. Moreover, the accuracy of flow modeling and other simulationtechniques may affect the performance prediction for wells in thesereservoirs and the ultimate decision to extract the natural resources.

SUMMARY OF THE INVENTION

Various embodiments of systems, methods, and computer-readable media areprovided for a near-well unstructured grid model builder for generatinga full-field unstructured grid for reservoir simulation. In someembodiments, a method for generating a near-well unstructured grid isprovided. The method includes receiving, by one or more processors,input data and determining, by one or more processors, a field polygonbased on the input data. The input data includes a structuredgeocellular model having a well or a structured reservoir simulationhaving a well or a structured reservoir simulation having a well andwell trajectory data and completion data for the well. The methodfurther includes determining, by one or more processors, a reservoirpolygon having a region of interest containing the well and generating,by one or more processors, a plurality of grid points. The plurality ofgrid points include a plurality of well grid points based on a firstgrid size and a plurality of other grid points outside of the region ofinterest based on a second grid size, the second grid size coarser thanthe first grid size. Additionally, the method includes performing, byone or more processors, a Delaunay triangulation based on the generatedgrid points and generating, by one or more processors, a Voronoi gridbased on the Delaunay triangulation. The method also includesgenerating, by one or more processors, a near-well unstructured gridbased on the Voronoi grid. Generating the near-well unstructured gridincludes generating a geometry of the near-well unstructured grid,generating properties of the near-well unstructured grid, and generatingperforation of the near-well unstructured grid.

In another embodiment, a non-transitory tangible computer-readablestorage medium having executable computer code stored thereon forgenerating a near-well unstructured grid is provided. The computer codehas a set of instructions that causes one or more processors to performthe following: receiving, by one or more processors, input data anddetermining, by one or more processors, a field polygon based on theinput data. The input data includes a structured geocellular modelhaving a well or a structured reservoir simulation having a well or astructured reservoir simulation having a well and well trajectory dataand completion data for the well. The computer code further includes aset of instructions that causes one or more processors to perform thefollowing: determining, by one or more processors, a reservoir polygonhaving a region of interest containing the well and generating, by oneor more processors, a plurality of grid points. The plurality of gridpoints include a plurality of well grid points based on a first gridsize and a plurality of other grid points outside of the region ofinterest based on a second grid size, the second grid size coarser thanthe first grid size. Additionally, the computer code further includes aset of instructions that causes one or more processors to perform thefollowing: includes performing, by one or more processors, a Delaunaytriangulation based on the generated grid points and generating, by oneor more processors, a Voronoi grid based on the Delaunay triangulation.The computer code further includes a set of instructions that causes oneor more processors to perform the following: also includes generating,by one or more processors, a near-well unstructured grid based on theVoronoi grid. Generating the near-well unstructured grid includesgenerating a geometry of the near-well unstructured grid, generatingproperties of the near-well unstructured grid, and generatingperforation of the near-well unstructured grid.

In another embodiment, a system for generating a near-well unstructuredgrid is provided. The system includes one or more processors and anon-transitory tangible computer-readable memory having executablecomputer code stored thereon. The computer code comprising a set ofinstructions that causes one or more processors to perform thefollowing: receiving, by the one or more processors, input data. Theinput data includes a structured geocellular model having a well or astructured reservoir simulation having a well or a structured reservoirsimulation having a well and well trajectory data and completion datafor the well. The computer code further includes a set of instructionsthat causes one or more processors to perform the following:determining, by the one or more processors, a reservoir polygon having aregion of interest containing the well and generating, by the one ormore processors, a plurality of grid points having a first grid size inthe region of interest. The computer code further includes a set ofinstructions that causes one or more processors to perform thefollowing: performing, by the one or more processors, a Delaunaytriangulation based on the generated grid points and generating, by theone or more processors, a Voronoi grid based on the Delaunaytriangulation. The computer code also includes a set of instructionsthat causes one or more processors to perform the following: generating,by one or more processors, a near-well unstructured grid based on theVoronoi grid and providing, over a network coupled to the one or moreprocessors, the near-well unstructured grid to a parallel reservoirsimulator. Generating the near-well unstructured grid includesgenerating a geometry of the near-well unstructured grid, generatingproperties of the near-well unstructured grid, and generatingperforation of the near-well unstructured grid.

In another embodiment, a non-transitory tangible computer-readablestorage medium having executable computer code stored thereon for aworkflow interface for generating a near-well unstructured grid isprovided. The computer code comprising a set of instructions that causesone or more processors to perform the following: define a workflowinterface for a near-well unstructured grid builder. The workflowinterface is configured to define input data for the near-wellunstructured grid builder and define gridding options for the near-wellunstructured grid builder. Additionally, the workflow interface isconfigured to display well data of the input data in a 2D or 3Dvisualization and provide well data and a region of interest within theinput data to an unstructured grid model builder for generation of anunstructured grid. Additionally, the workflow interface is configured todisplay geometry of the generated unstructured grid, display theproperties of the generated unstructured grid, and display theperforation of the generated unstructured grid.

In yet another embodiment, a computer-implemented method forconstructing an unstructured grid is provided. The method includesreceiving, by one or more processors, a structured grid having a firstplurality of grid points and a well of a reservoir, and determining, byone or more processors, a region of interest in the structured grid. Themethod further includes generating, by one or more processors, a secondplurality of grid points in the region of interest according to a firstgrid size and constructing, by one or more processors, a 2.5Dunstructured grid from the second plurality of grid points and the thirdplurality of grid points. Additionally, the method includes processing,by one or more processors, the 2.5 unstructured grid via a reservoirsimulator to produce a simulation of the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system for generating a near-wellunstructured grid and performing a full field unstructured gridreservoir simulation in accordance with an embodiment of the presentinvention;

FIG. 2 is a block diagram of the near-well unstructured grid modelbuilder of FIG. 1 in accordance with an embodiment of the presentinvention;

FIG. 3 is a block diagram of the parallel reservoir simulator of FIG. 1in accordance with an embodiment of the present invention;

FIG. 4 depicts an example of a well grid with quad tree local gridrefinement for two vertical wells and one horizontal well in accordancewith an embodiment of the present invention;

FIG. 5 depicts an example of a complex well with two levels of quad-treeLGR and well grid points in accordance with an embodiment of the presentinvention;

FIG. 6 depicts a complex well with two levels of quad tree LGR and withone parallel track of grid points on both sides of the well points;

FIG. 7 depicts an example of a Delauney triangulation of a planar pointset in accordance with an embodiment of the present invention;

FIG. 8 depicts an example of the perpendicular bisection of the Delauneytriangulation of FIG. 7 to generate Voronoi cells in accordance with anembodiment of the present invention;

FIGS. 9A and 9B depict an example of a full-field unstructured gridhaving two hundred and thirty-three history wells in accordance with anembodiment of the present invention;

FIGS. 10A and 10B depict a close-up 2D view of the complex wellbores andthe corresponding near-well grids respectively for a window area nearthe middle part of a full field unstructured grid with 233 historycomplex wells and 395 future complex wells in accordance with anembodiment of the present invention;

FIG. 11 is a schematic diagram of a computer implementing a workflowinterface in accordance with an embodiment of the present invention;

FIGS. 12A and 12B are block diagrams of a process of the workflowinterface in accordance with an embodiment of the present invention;

FIGS. 13A and 13B are block diagrams of a process of the workflowinterface in accordance with an embodiment of the present invention;

FIGS. 14A and 14B are block diagrams of a process for using thenear-well unstructured grid model builder in accordance with anembodiment of the present invention;

FIG. 15 is a block diagram of a system implementing a near-wellunstructured grid model builder in accordance with an embodiment of thepresent invention;

FIG. 16 is a block diagram of a computer in accordance with anembodiment of the present invention; and

FIGS. 17-34 depict various steps of a process for generating a near-wellunstructured grid model using the system of FIGS. 1-3 in accordance withan embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but to the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION

As described further below, systems, methods, and computer-readablemedia are provided for a near-well unstructured grid model builder forgenerating a near-well unstructured grid for full-field reservoirsimulation in accordance with an embodiment of the present invention. Asdescribed further below, the near-well unstructured grid model buildermay include a workflow interface and a parallel unstructured grid modelbuilder. The inputs to the near-well unstructured grid model builder mayinclude existing well trajectory and completion data, future well data,a geological model, a structured grid simulation model, or anycombination thereof.

The workflow interface of the near-well unstructured grid model buildermay set user preferences and gridding options such as inputs and gridsizes. The workflow interface may include 2D and 3D rendering tools thatvisualize the well data and enable a user to view a field polygon. Auser may use the workflow interface to create a reservoir polygon havingregions of interest in the field polygon. The workflow interface maythen provide a job interface for submission of jobs to the parallelunstructured grid model builder and monitoring of the jobs.

The parallel unstructured grid model builder constructs an unstructuredgrid based on the data and gridding options defined via the workflowinterface. The parallel unstructured grid model builder analyzes thewell trajectory and perforation data for compatibility and samples welltrajectory points contained by the perforation start and end pointsbased on the grid size to produce well grid points. The parallelunstructured grid model builder then generates and optimizes gridpoints, and the generation may include multi-level local gridrefinement. Additionally, well grid points are computed and grid pointsare assigned weights, such that the well grid points may have higherweights than the close quad-tree local grid refinement points.Additionally, in some embodiments parallel grid points are placed onboth sides of the well grid points. The parallel unstructured grid modelbuilder further includes an unconstrained Delauney triangulation usingthe generated grid points. After the Delaunay triangulation, theparallel unstructured grid model builder generates a Voronoi grid(Voronoi cells) using perpendicular bisection of the triangle edges ofthe Delaunay triangulation. Next, the parallel unstructured grid modulebuilder generates the unstructured grid geometry, the unstructured gridproperties, and the unstructured grid perforation.

The workflow interface also enables a user to view and evaluate thegenerated unstructured grid geometry, the unstructured grid properties,and the unstructured grid perforation. The generated unstructured gridgeometry may be displayed in a rendering tool of the workflow interface.The generated unstructured grid properties may be displayed in aproperty analysis tool of the workflow interface, and the generatedunstructured grid perforation may be displayed in a perforation analysistool of the workflow interface. Additionally, the workflow interface mayinclude a region data constructer for constructing unstructured regiondata from structured region data selected by a user.

The unstructured grid generated by the near-well unstructured gridbuilder may be provided to a parallel reservoir simulator for reservoirsimulation. The output from the parallel reservoir simulator may beprovided to a results viewer and data analyzer for post-simulationanalysis and visualization. An inputted geological model may be updated,or additional local regridding may be performed based on the analysis.Additionally, the reservoir simulation results may be provided to anassisted history match tool to perform a model update or to performsensitivity analysis.

FIG. 1 depicts a system 100 generating a near-well unstructured grid andperforming a full field unstructured grid reservoir simulation inaccordance with an embodiment of the present invention. As used herein,the term “near-well unstructured grid” refers to an unstructured gridgenerated according to the techniques described herein. As shown in FIG.1, the well trajectory and completion data 102 for wells in a reservoirmay be obtained. The well trajectory and completion data may be obtained(e.g., exported) from a well database having well trajectory survey dataand completion data with time and completion intervals. The welltrajectory data may include sets of x-y-z spatial points describing thewellbore spatial locations of each branch of each well (e.g.,conventional or complex MRC wells). The completion data may include thestart and end points of each completion interval along the wellbores andthe time intervals when that completion is open to flow.

Additionally, future well data 104 (e.g., well trajectory data forfuture wells) may be obtained. The future well data may include data forplanned future wells in a reservoir and may be in various formats, suchas an ASCII data file, an existing structured grid reservoir simulationmodel recurrent data file, or other suitable formats. The system 100also includes a structured geological model 106 (also referred to as a“geocellular model”) obtained from a geological modeling process. Insome embodiments, the structured geological model 106 is constructedfrom a geocellular model for a field for the purpose of reservoirsimulation. The structured geological model 106 may describe thegeometry and property data for one or multiple reservoirs. Further, astructured grid simulation model 108 is also obtained. In someembodiments, the structured grid simulation model 108 is generated byupscaling the structured geological model 106. In such embodiments, themodel geometry of the structured grid simulation model 108 may bedefined by corner point geometry (CPG) format or variable-depthvariable-thickness Cartesian (IJK) grid format. In some embodiments, thestructured grid simulation model 108 may be a previously history matcheddataset or may be partially matched dataset.

As described further below, the data 102, and the model 106, the model108, or both, are provided as inputs to a near-well unstructured gridmodel builder 110. Additionally, in some embodiments the future welldata 104 is provided as input to the near-well unstructured grid modelbuilder 110 for performance prediction. The near-well unstructured modelbuilder 110 is illustrated in FIG. 2 and described in further detailbelow. The system 100 may also include a parallel reservoir simulator112 for performing a reservoir simulation based on the unstructured gridmodel generated by the near-well unstructured grid model builder 110. Anembodiment of the parallel reservoir simulator 112 is illustrated inFIG. 3 and described further below. In some embodiments, the parallelreservoir simulator 112 may be the GigaPOWERS™ simulator manufactured bySaudi Aramco of Dhahran, Saudi Arabia. The parallel reservoir simulator112 may perform a reservoir simulation using the near-well unstructuredgrid generated by the near-well unstructured grid model builder 110.

In some embodiments, the system 100 may also include an assisted historymatch (AHM) tool 114. The AHM tool 114 may perform simulation modelupdates for reservoir history match processing or may performsensitivity analyses over a range of parameters to determinate theresponse surface of the reservoir simulation. In some embodiments, theAHM tool 114 may generate multiple simulation data sets which can besubmitted to the parallel reservoir simulator 112. For example, eachsimulation for each such simulation data sets may each be a parallel jobrunning on an assigned group of computation nodes in high performancecomputing (HPC) system. In some embodiments, the AHM tool 114 mayreceive MODIFY statements (described further below) generated by thenear-well unstructured grid model builder 110.

Additionally, in some embodiments the system 100 may include anunstructured grid reservoir simulation result viewer and data analyzer116. The result viewer and data analyzer 116 may include an importengine to input the results (e.g., result files) from the parallelreservoir simulation 112 for post simulation analysis and visualization.In some embodiments, the structured geological model 106 may be updatedbased on the analysis and visualization provided by the results viewer.Additionally, in some embodiments, the near-well unstructured grid modelbuilder 110 may perform regridding or generate additional MODIFYstatements for further history matching based on the output from theresults viewer and data analyzer 116. Further, in some embodiments,additional simulations may be performed by the parallel reservoirsimulator 112 based on the output from the results viewer and dataanalyzer 116.

FIG. 2 depicts the near-well unstructured grid model builder 110 infurther detail in accordance with an embodiment of the presentinvention. The near-well unstructured grid model builder 110 may includea workflow interface 200 and a parallel unstructured grid model builder202. As described further below, the parallel unstructured grid modelbuilder 202 may be implemented on one or more computers in variousarrangements for parallel processing. In some embodiments, the workflowinterface 200 may be implemented as a graphical user interface (GUI)having windows, menus, icons, toolbars, and other components to providevarious graphical functionalities. Such graphical functionalities mayinclude, for example, drawing, 2D and 3D rendering, object selection,camera manipulation control (e.g., via a mouse), interactive dialogboxes, and other graphical functionalities. In some embodiments,interactive dialog boxes enable communication between the near-wellunstructured grid model builder 110 and a user. In such embodiments, theinteractive dialog boxes may enable a user to execute user specificcommands, display computation results, and prompt a user (e.g., via asub-window) to respond to requests for data or instructions. Theworkflow interface 200 enables definition and visualization of the inputdata to the near-well unstructured grid model builder 110 before theinput data is provided to the parallel unstructured grid model builder202 for further processing. Advantageously, the workflow interface 200provides functionalities and tools to the user in an intuitive manner sothat the unstructured grid model building tasks may be launched andcompleted from the workflow interface 200 without additional complexityof other interfaces or switching outside of the user's computingenvironment.

As described above, the near-well unstructured grid model builder 110may receive various gridding inputs, such as the existing welltrajectory and completion data 102, the future well data 104, thestructured geological model 106, the structured grid simulation model108, or different combinations thereof. The workflow interface 200 mayenable a user to set gridding inputs and user preferences (block 204).For example, a user may specify the gridding input data sources forobtaining the inputs described above, various user preferences, andvarious gridding options. In some embodiments, for example, thisfunctionality may be provided by a tab widget that providesvisualization of the user settings and data viewing functions viabuttons or other user interface elements. In some embodiments, thegridding options may include the polygon and grid size for each of theregions-of-interest of the wells input to the near-well unstructuredgrid model builder 110. In some embodiments, the initial grid size forthe regions of interest may be set based on the geological model 106 orthe structured grid simulation model 108 and, in such embodiments, theinitial grid points may be the cell center points of the geologicalmodel 106 or the structured grid simulation model 108 projected on a 2Dgridding plane within the regions of interest. Otherwise, the grid pointdistribution described below may be generated based on theuser-specified grid size.

In some embodiments, the default polygon may be the field polygon basedon the structured grid and coordinate system obtained from thegeological model 106 or the structured grid simulation model 108. Forexample, the field polygon may be a 2D representation of the geologicalmodel 106 that defines the simulation domain where the reservoirs andwells are contained and the corresponding region to be gridded andstudied. The near-well unstructured grid model builder 110 may bedefined with the field rectangle polygon at the coarsest grid levelfollowed by one or more multiple reservoir polygons for each reservoirin the field. Additionally, local grid refinement regions may be addedwithin the reservoir regions to further refine grids in regions ofinterest. As described further below, the near-well unstructured gridmodel builder 110 includes techniques for boundary conforming grids ofthe near-well regions at the well bore using multi-level quad treeprocesses, which provide smooth grid transition from well grids toreservoir grids, or the inter-wellbore grid.

After the field polygon has been defined, the well data may bevisualized by a 3D renderer (block 206). For example, the welltrajectory and completion data may be visualized in a 3D UniversalTransverse Mercator (UTM) coordinate system. In some embodiments, thewell path and perforations may be extracted from the existing welltrajectory and completion data 102 and, in some embodiments, the futurewell data 104. In some embodiments, the visualization of 3D well datamay include drawing the well path and peroration using user-selectedcolors specified in step 204 (e.g., in a tab widget). Additionally, insome embodiments the displayed completion open and close of the well maybe based on completion dates in the existing well trajectory andcompletion data 102 and a simulation interval specified by the user instep 204. FIG. 17 illustrates an example of the visualization of welldata in 3D in accordance with an embodiment of the present invention.

The well data may be visualized on top of the field polygon and may beviewed in 2D and 3D. In the 3D view, the top depth and bottom depth ofthe geological model 106 may be displayed such that well locations maybe easily viewed. The 3D viewer of the workflow interface 200 mayinclude camera manipulation and zooming to enable easy viewing controlsvia a mouse, keyboard, or other suitable input devices. The camera ofthe 3D viewer may responds instantly to changes in the viewing optionsand zooms to show all of the wells of interest in the view whileproviding sufficient geometry details. Additionally, when viewingindividual well options, the user may sequentially scroll each well viathe keyboard (or other input device) and may jump to select a differentwell via the mouse (or other input device) such that only a selectedwell is displayed. In response to these user actions, the cameraorientation and focal point will be automatically adjusted to move tothe well with a correctly computed zoom so that sufficient geometrydetails are viewable for close examination by the user. Advantageously,the 3D viewer enables fast and effective viewing of all wells, groups ofwell, or individual wells, Consequently, the visualization of 3D data(e.g., wells, top and bottom horizons of a model, and the field polygon)enables examination of the well locations in the field domain so thatthe consistency of the well data extracted from the existing welltrajectory and completion data 102 and the future well data 104 may beverified against the coordinate system obtained from the geologicalmodel 106 and the structured grid simulation model 108.

After the well data is visualized, additional gridding inputs, options,and user preferences may be set (block 204) by a user based evaluationof the visualized well data. The reservoir polygon may be initiallydesigned as a 2D polygon with any shape (e.g., irregular) inside of thefield polygon while covering all of the wells. A user may use aninteractive drawing tool provided in the workflow interface 200 toconnect points (e.g., defined via mouse clicks) on the field polygon andautomatically close the polygon with the first and last points. Thereservoir polygon may define the regions-of-interest for the near-wellunstructured grid model builder 110, and the field polygon may definethe domain volume in which the reservoir simulation is conducted. Forexample, the reservoir polygon may define the region occupied by eachreservoir in the domain volume. Accordingly, the field polygon and thereservoir polygon divide the simulation domain so that the simulationcan be concentrated on the near-well regions within the reservoirpolygon. FIG. 18 illustrates an example of a field polygon and areservoir polygon defining regions of interest for the near-wellboreunstructured grid model builder 110 in accordance with an embodiment ofthe present invention. Additionally, as described above, a coarse gridsize may be specified for the field polygon while finer grid sizes areapplied on the reservoir polygons and the wellbores. Advantageously,this multi-level gridding strategy provides for the spacing of gridpoints in a particular region to be determined by the grid size of thatregion, but grid points are prioritized based on importance. Asdescribed further below, point priority may control the removal andadjustment of points of the parallel unstructured grid model builder202.

After regions of interested are identified and other gridding optionsare set and well data is verified, parallel model building jobs aresubmitted by a user and received (block 208) via a job interface. Thejob interface may also enable a user to submit and monitor the parallelmodel building jobs. As described further below, the parallel modelbuilding jobs may be submitted to the parallel unstructured grid modelbuilder 202. In some embodiments, for example, the parallel unstructuredgrid model builder 202 may be executed on a high performance computing(HPC) cluster.

Within the parallel unstructured grid model builder 202, theunstructured gridding data input to the builder 202 may be processed(block 210). For example, the unstructured gridding data may be verifiedand provided for further processing by the parallel unstructured gridmodel builder 202. Additionally, in some embodiments, I/O errorhandlings are processed. For example, the processing may includeverifying whether a defined reservoir polygon is contained in the fieldpolygon and if there is any perforated wells outside of the reservoirpolygon. Further, in some embodiments the processing may includeverifying if required options are complete, such as a grid size for eachregion of interest, and so on. The processing may ensure that thegridding options and data are complete and valid so that the modelbuilding may progress without errors.

After the gridding options and input data is processed, the welltrajectory and perforation data obtained from the existing welltrajectory and completion data 102 and future well data 104 is analyzed(block 212). The analysis may include verifying the compatibilitybetween the well trajectory data and the perforation data to ensure thewell perforation adheres to the well trajectory. Any errors detected bythe analysis may be reported, such as in the workflow interface 200.After the verification is complete, the well trajectory points containedby the perforation start and end points may be sampled based on the gridsize in the regions of interest. The sampled trajectory points are wellgrid points used in subsequent processing. Advantageously, the samplingaccounts for the complicated well paths that may involve multiplecurves, by using measured depth values to track the perforations alongthe well path. Moreover, the sampling may keep all the points necessaryto adhere to the well trajectory but also skip unnecessary points whenthe well paths are straight.

Next, the grid points of the unstructured grid are generated (block214). As described below in paragraphs [0047]-[0052], full-fieldunstructured gridding may be performed. The gridding steps may includethe following: generating field grid points having a field grid size afirst weighting; generating reservoir grid points having a reservoirgrid size and a second weighting; generating well grid points having awell grid size and a third weighting; performing a multi-level quad treelocal grid refinement in the near-well regions inside the reservoirpolygon; removing grid points using the assigned weightings; performingan unconstrained Delaunay triangulation; generating a Voroni grid viaperpendicular bisection of the external boundary of the field domain;detecting and removing degenerate edges of the Voroni grid; and buildinga 3D volume using the 2.5D unstructured grid geometry.

As described above, grid point within the regions of interest may begenerated based on the cell center point of the structured geologicalmodel 106 or the structured grid simulation model 108 or based on a userspecific grid size for the regions of interest. For grid points outsidethe region of interest, the grid points may be generated based on auser-specified background grid size. FIG. 19 depicts an example of thegeneration of grid points of the unstructured grid in accordance with anembodiment of the present invention. The generation may includeassigning weights (also referred to as “priority”) to the grid pointsand using the weights to adjust or remove conflicting grid points for agood grid quality measure for the entire domain. In some embodiments,generating the grid points may include the following: (1) gridding thereservoir polygon and the region of the field polygon outside of thereservoir polygon based on the region grid size (e.g., spacing)specified by the user (as described in block 204 and for example, may bethe Cartesian simulation grid spacing), and (2) applying a multi-levelquad tree local grid refinement (LGR) in the near-well regions insidethe reservoir polygon to create smooth grid transitions from highresolution well grids to reservoir grids. FIG. 20 illustrates an exampleof such a multi-level quad tree LGR technique in accordance with anembodiment of the present invention. In some embodiments, the number oflevels and distance measure of the multi-level quad tree local gridrefinement (LGR) may be specified by the user. An example of a well gridwith quad tree LGR for two vertical wells and one horizontal well isdepicted in FIG. 4. As described above, the sampled well trajectorypoints may provide well grid points. The well grid points are evenlydistributed points based on a user-specified well point spacingparameter. Well grid points for the well tree may be computed for thecompletion part of the well, i.e., the portion of the well tree open toflow in the reservoir. Portions of the well borehole not completed maybe removed from the well grid point generation.

An example of a complex well with two levels of quad-tree LGR and wellgrid points is depicted in FIG. 5. As will be appreciated, the gridrefinement may improve grid quality and appropriately stage the gridresolution for the near-wellbore flow and transport calculations. FIG.21 illustrates an example near-wellbore refined grid points shown withthe projected well-bore trajectory in accordance with an embodiment ofthe present invention, and. As can be seen in these figures, the refinedgrid points near the wells do not adhere to the well trajectory as theyare the grid points directly generated for the reservoir polygon FIG. 22depicts an example of a well tree in accordance with an embodiment ofthe present invention, and FIG. 23 depicts the well grid points for thewell tree of FIG. 22. FIG. 24 depicts an example of a near-wellboreregion grid point distribution and point removal and adjustment inaccordance with an embodiment of the present invention, and FIG. 25illustrates the wellbore trajectory in relation to the near-wellboregrid depicted in FIG. 24. In some embodiments, parallel near-wellborepoints may be placed on both sides of the well points to improve themodeling of near well flow. The parallel near-wellbore points areweighted higher than the quad-tree refinement points but below the wellpoints. An example of a complex well with two levels of quad tree LGRand with one parallel track of grid points on both sides of the wellpoints is depicted in FIG. 6. The grid point generation may also includeoptimization of grid points for the whole domain according to theweighting. For example, grids points are adjusted and removed toguarantee adjacent well points connected to the formed triangle's edgesof the subsequent unconstrained Delauney triangulation described below.Additionally, well grid points may displace other grid points whichviolate grid quality metrics or the empty circumcircle of the Delauneytriangle edges on the well paths. For example, grid points having alower weighting are removed when the spacing requirement is violated forthe region. FIG. 26 illustrates an example of the multi-level gridpoints for the field grid, reservoir grid, and near-wellbore regiongenerated by placing near-wellbore points on both sides the well pointsand weighting of the parallel points in accordance with an embodiment ofthe present invention.

Next, the generated grid points are used to perform an unconstrainedDelauney triangulation of the entire field domain, and the Delauneytriangulation is used to generate Voronoi grid cells (block 216). Anexample of a Delauney triangulation of a planar point set is depicted inFIG. 7. The Delauney triangulation forms the primal grid from which adual grid for Voronoi cells is generated via bisecting the edges of thetriangles of the Delauney triangulation. FIG. 8 depicts an example ofthe perpendicular bisection of the Delauney triangulation of FIG. 7 togenerate Voronoi cells. Perpendicular bisection (PEBI) on the externalboundary of the field domain produces infinite rays that interact withthe field boundaries, and these intersections are the Voronoi cellvertices on the external boundary of the field domain. The Voronoi cellsare used to compute the 2.5D finite volumes for reservoir simulation.Additionally, in some embodiments, the degenerate edges may be detectedand removed to produce a corrected PEBI grid (also referred to as“Voronoi grid” or “Voroni dual grid”) suitable for reservoir simulation.

Next, the geometry, properties, and perforations of an unstructured grid(e.g., a 2.5D unstructured grid) are generated. As shown in FIG. 2, theunstructured grid geometry is generated (block 218). The generation mayinclude projecting the 2D PEBI grid vertex coordinates of the PEBI grid(Voronoi grid) constructed in block 216 onto each horizon of thegeocellular model of the structured grid simulation model to compute thedepths to the bounding surfaces of each grid layer. This generates a2.5D unstructured grid geometry for the entire domain, preserves thelayer geometry of the geological model 106 or the structured gridsimulation model 108, and accounts for the geological layering of thereservoir. Additionally, in some embodiments, a graph of theconnectivity description of the Voronoi cells, the Voronoi vertexcoordinates, and the cell to vertices references are also produced.

Additionally, the unstructured grid properties are generated (block220). The property values of each unstructured cell for each propertydescribed in the inputted structured grid geological model 106 or thestructured grid simulation model 108 are computed and assigned. In someembodiments, for properties having an integer type, point injection fromthe structured grid value is applied onto the unstructured grid cellcenter. In some embodiments, for laterally correlated properties such asporosity, permeability, and other properties, the property values may beinterpolated or injected. For uncorrelated properties, such as fractureparameters, the property values are point injected. The computedproperty maps resemble the input structured grid geocellular model orthe structured grid simulation property maps. Additionally, in someembodiments, generating the unstructured grid properties includesvolume-in-place correction on a layer by layer basis to closelyreproduce the total pore-volume of the original structured griddescription.

The unstructured grid perforation is also generated (block 222). Thegenerating includes computing the intersection points of each wellboretrajectory with the finite volume cell faces of all the grid cellspenetrated by the wellbore. The entry-exit location may be on any of thevertical or the lateral cell faces of the finite volumes determined bythe unstructured grid geometry (generated in block 218). The perforationmay be generated as a perforated cell list and the entry-exitcoordinates for each perforated cell. In some embodiments, theperforation is stored as a file to form a part of the recurrent data ofthe simulation model data. This data is used by the parallel reservoirsimulator to calculate a well index (WI) for each perforated grid cellwhich is the connection factor for the well terms in the flowcalculation of the reservoir simulation mass and energy balances of thesystem.

After generating the unstructured grid geometry, properties, andperforations via the parallel unstructured model builder 202, theunstructured grid may be provided to the workflow interface where thegridding results may be analyzed and verified before the unstructuredgrid is provided to the parallel reservoir simulator 112. The Voronoicells and grid points of the generated unstructured grid geometry may bedisplayed by a 2D rendering tool (block 224). In some embodiments, theVoronoi cells and Delauney triangulation grid points may be displayedaccording to user-selected colors. The displayed Voronoi cells and gridpoints may enable a user to examine the correlation between the cellsand the grid points to verify the generated unstructured grid. The 2Drendering tool of the workflow interface may enable a user to zoom inand out and visually evaluate the Voronoi cells and grid points inrelation to the well trajectory and perforation data. FIG. 28illustrates an example of a zoomed view of Voroni cells and grid pointsin relation to the well trajectory and perforation data. For example, auser may zoom in to examine the Voronoi cells near a well tree. FIG. 27depicts an example of a zoomed view of Voroni cells near the well treeof FIG. 25 in accordance with an embodiment of the present invention. Ina typical generated unstructured grid and as shown in these figures, forexample, the well grid points may be observed exactly at the centers ofthe Voronoi cells while the Voronoi centers adhere to the complex welltrajectory. FIG. 29 illustrates an example of a view of grid cells inrelation to the well trajectory and completion without the grid pointsin accordance with an embodiment of the present invention.Advantageously, the 2D rendering tool of the workflow interface 200 mayshow the grid points of each sub-step of the grid point generation andoptimization, in addition to the showing the Voronoi cells and themerged grid points. Thus, the grid points at each optimizing stage ofthe grid point optimization may be examined. Furthermore, the grid cellsize variation from the field to the reservoir, then to thenear-wellbore regions, may be displayed, with or without the well-tree,by the visualization tool. FIG. 30 depicts an example of a 2D viewshowing the field grid, reservoir grid, and near-well grid without thewell tree and FIG. 31 depicts an example of a 2D view showing the fieldgrid, reservoir grid, and near-well grid with the well tree The 2Drendering tool of the workflow interface thus enables validation of theconsistency and quality of the multi-level unstructured gridding,validation of the grid point weighting, and visual confirmation of thelayout of well grid cells along the well trajectory.

Additionally, the generated unstructured grid properties may bedisplayed for analysis by an analysis tool of the workflow interface(block 226). The analysis tool may enable validation of the propertiesgenerated for the unstructured grid (in block 220). In some embodiments,the analysis tool may display the properties at each unstructured gridcell at each geological grid layer using color mapping. Additionally, insome embodiment the analysis tool includes a dropdown list to enableselection of individual properties for examination. Further, more thanone grid layer may be visualized at the same time so that the propertyvalues across grid layers may be observed. The analysis tool aids invalidating the generating the unstructured grid properties, such asporosity, permeability, fluid saturations and so on. For example, anydefects in the near-well unstructured grid may be detected by theanalysis tool of the workflow interface 200.

The qualities of the generated unstructured grid perforation data may bedisplayed for analysis by a perforation analysis tool of the workflowinterface 200 (block 228). The perforation analysis tool may draw all ofthe intersected cells generated by the unstructured grid model builder,and the drawing may be performed based on user-selectable viewingoptions, such as viewing all wells, groups of wells, or one individualwell. The perforated cells may be highlighted in the perforationanalysis tool and the exit-entry points of the well trajectory can bedisplayed. In some embodiments, the intersected cells are drawn alongwith the corresponding well perforation path in 2D and 3D, and theintersected points on the cell faces may also be shown. FIGS. 32-34depict various views created by the perforation analysis tool. FIG. 32illustrates an example of a 2D view showing the perforated cells of wellin accordance with an embodiment of the present invention. Additionally,FIG. 33 illustrates an example of a 3D view showing the perforated cellsof well in accordance with an embodiment of the present invention. FIG.34 further illustrates an example of a 3D view of all the unstructuredcells perforated by wells within the 3D view in accordance with anembodiment of the present invention. When rendered in 2D, theintersected cells and points may be evaluated against the finite volumecells in the generated unstructured grid geometry and analyzed in the 2Drendering tool. Advantageously, the perforation analysis tool makes thevisual examination of the generated perforation data of the unstructuredgrid easy and interactive.

After any further analysis in the workflow interface is complete, thegridding results of the near-well unstructured grid model builder may beoutputted from the parallel unstructured grid model builder and providedto the parallel reservoir simulator 112. FIG. 9A depicts an example of afull-field unstructured grid having over two hundred and thirty threehistory complex wells and generated according to the techniquesdescribed herein. FIG. 9B depicts a close-up view of the near-well gridsfor a window area near the southern tip of the full field unstructuredgrid of FIG. 9A.

Additionally, FIG. 10A depicts a close-up 2D view of the complex wellbores for a window area near the middle part of the full fieldunstructured grid having two hundred and thirty three history complexwells and three hundred and ninety five future complex wells. FIG. 10Bdepicts a close-up 2D view of the corresponding near-well grids for awindow area near the middle part of the full field unstructured gridhaving two hundred and thirty three history complex wells and threehundred and ninety five future complex wells. In some embodiments,MODIFY regions are constructed by a MODIFY unstructured region dataconstructor (block 230) from converted data or from user selections. Asused herein, the term “MODIFY” relates to region data that is a part ofMODIFY statements used by simulation engineers to specify cell lists toapply property modifiers to update reservoir model data for historymatching or sensitivity study purposes. In some embodiments, the MODIFYunstructured region data constructor may provide an interface forconverting a MODIFY region from structured grid format to unstructuredgrid format. Additionally, in some embodiments the MODIFY unstructuredregion data constructor also provides an interface for enabling a userto select unstructured grid cells or regions directly from the scene andbuild unstructured region data visually. The MODIFY unstructured regiondata constructor provides for conversion from a region formats betweenstructured grids and unstructured grids. In some embodiments, forexample, MODIFY statements are not used in the parallel reservoirsimulator 112 and the region format conversion is not used. The MODIFYunstructured region data constructor enables porting of the historymatch work from the structured grid to the near-well unstructured grid.For example, when conducting history match in the unstructured grid, theunstructured MODIFY region data may be constructed directly via theinterface. The unstructured region data may also be used when theunstructured gridding workflow is obtained directly from the geologicalmodel 106. The interface of the unstructured gridding MODIFYunstructured region data constructor enables selection of groups of gridcells (e.g., via “rubber-band selection”). For example, a group of cellsin 2D may be selected, and a 3D box type region is constructed after the3D layer range for the selected cells is specified. The created regionis then used as the location for which the simulation MODIFY conditionsand expressions are applied.

Advantageously, the workflow interface 200 and the parallel unstructuredgrid model builder 202 described above provide an easy and communicativeworkflow for processing complex reservoir and well geometry. Forexample, in field-scale reservoir simulation, the number of complex MRCwells can range from the several hundred to several thousands. Beforebuilding the unstructured grid on all the reservoir and complex wells inthe field, the workflow interface 200 and the parallel unstructured gridmodel builder 202 enable selection of a small group of wells andgeneration of unstructured grids on the selected wells. This results ineasier and faster reservoir simulation with higher quality. Bysimplifying the unstructured grid complexity the compatibility check ofthe well data, geological model, regions of interest, and other griddinginputs may be performed faster. For example, the grid size specified onthe regions of interest may not be compatible and coordinated; thus, thegrid model builder can quickly generate unstructured grids to tune thegridding control data. The unexpected grid resolution can be determinedquickly as compared to building the full-field model completely on allreservoirs and wells. After initial building is complete, theunstructured grid may be verified in the workflow interface and providedto the parallel reservoir simulation for a trial simulation. After thetrial simulation, all reservoir and wells can be incorporated in acomplex field-scale unstructured grid having a longer build time.

It should be appreciated that the workflow interface 200 and parallelunstructured grid model builder 202 may generate unstructured grids onall the reservoirs and wells in a field but may also build theunstructured grid only on a portion of the field, such as a particularreservoir with a subset of the included wells. Moreover, by building anunstructured grid only on a portion of the field, validation of thevisualized 3D well data and setting of the proper gridding options iseasier for a user. Moreover, defects may be more easily detected andresolved by reviewing the unstructured grid geometry, properties, andperforation data in the workflow interface 200. Advantageously, theworkflow interface 200 and parallel unstructured grid model builder 202speed up the building time of full-field model building having largenumbers of MRC wells and makes large scale simulation of unstructuredgrids with high resolution near wellbore modeling efficient andpossible.

FIG. 3 depicts a block diagram of the parallel reservoir simulation 112in accordance with an embodiment of the present invention. As describedabove, the near-well unstructured grid from the near-well unstructuredgrid model builder 110 is provided to the parallel reservoir simulation112. In some embodiments, the parallel unstructured grid reservoirsimulation may include a sequence of time steps over the history matchperiod, the prediction period, or both. As mentioned above, the parallelreservoir simulator may be executed on HPC cluster, e.g., an HPC clusterhaving several computing nodes each having multiple CPUs, with orwithout accelerator devices such as GPGPUs or MIC.

The parallel reservoir simulation 112 may receive, as input, theunstructured grid as constructed by the unstructured grid model builder(block 300). In some embodiments, the input process for the parallelreservoir simulation 112 may be a data parallel reader such that eachprocess of the assigned group of processes read a partition of nearlyequal subset of grid cell information for further processing. In suchembodiments, during this process, the grid cells which have less thanminimum thickness (a pinch-out cell) or less minimum pore-volume orporosity (a dead cell) are flagged as null cells. The grid cells whichare not null cells may be the active cells included in the reservoirsimulation step.

Next, the data parallel construction of the 3D distributed connectivitygraph for the active cells is performed (block 302). The graph may bedistributed (e.g., by load-balancing) across the assigned group ofcompute processes for running parallel reservoirs simulation. In someembodiments, load balancing may be based on the equal division of globalactive cells into the individual compute processes, such that eachprocess contains a contiguous subdomain of active grid cells for thesimulation. Additionally, the subdomain boundary cell faces areminimized to reduce network communication requirements for theprocessors (and computing nodes) of a parallel computing environment,such as an HPC cluster. Additionally, a connection factor is alsocalculated that prescribes the strength of each connection based on theindividual cell permeability tensor and geometry of the neighboring celland cell faces. In some embodiments, the connection factor may also bereferred to as “transmissibility.”

Next, a reservoir simulation is performed (block 304) by the parallelreservoir simulation 112. For example, in some embodiments the reservoirsimulator uses a unified unstructured data infrastructure, formulation,and linear solver for both structured grid and unstructured gridsimulation. Finally, the simulation results may be outputted (block306), such as by an output process of the parallel reservoir simulation112. The simulation results may be written to a non-volatile storage(e.g., a hard disk) for post processing and analysis. In someembodiments, the output process is a parallel data write such that eachprocess of the assigned group of compute processes writes a partition ofnearly equal subset of grid cell information to disk storage.

As shown in FIG. 1, the output from the parallel reservoir simulator 112may be provided to the AHM tool 114 and the result viewer 116. The AHMtool 114 may use the MODIFY statements to perform model updates for thereservoir history match processing or to perform sensitivity analysisover a range of parameters, such as to explore the response surface ofthe simulation model. Various types of history matching may be used,including history matching that uses the MODIFY statements for modelupdating. As mentioned above, the AHM tool 114 may create multiplesimulation datasets that can be submitted to the parallel reservoirsimulator 112 in parallel (e.g., so that each simulation is a parallelcomputer job running on the computing nodes of a computing environment,such as an HPC cluster).

As also shown in FIG. 1 and mentioned above, the output from theparallel reservoir simulator 112 may also be provided to the 3Dunstructured grid reservoir simulation results viewer and data analyzer116. The 3D unstructured grid reservoir simulation results viewer anddata analyzer 116 may include an import engine to input the simulationresults files for post simulation analysis and visualization. Asmentioned above, the results of such analysis may be provided to updatethe geological model 106, to the near-well unstructured grid modelbuilder 110 for local regridding to generate additional MODIFYstatements, or to the parallel reservoir simulator 112 for additionalsimulation. It should be appreciated that this iterative workflow maycontinue until the desired history matching and evaluation have beencompleted.

FIG. 11 depicts a computer 1100 implementing the workflow interface 200in a graphical user interface 1102 in accordance with an embodiment ofthe present invention. As shown in FIG. 11, a user 1104 may interactwith the computer 1100 and the graphical user interface 1102. In someembodiments, the workflow interface 200 may be implemented on a computer1100. However, in other embodiments, the graphical user interface 1102may be implemented on multiple computers in communication with eachother over a network. Such embodiments may include, for example, aclient/server arrangement of computer, a peer-to-peer arrangement ofcomputers, or any other suitable arrangement that enables execution ofthe graphical user interface 1102. In some embodiments, the graphicaluser interface 1102 may implemented as a computer program stored on amemory of the computer 1100 and executed by a process of the computer1100.

FIG. 11 illustrates various components of the graphical user interface1102 that provide the functionality described above with regard to theworkflow interface 200. It should be appreciated that the graphical userinterface 1102 may be implemented using various user interface elements,such as windows, icons, controls such as buttons, switches, sliders, andso on, dialog boxes, tabs, and any other suitable user interfaceelements. As shown in FIG. 11, the graphical user interface 1102includes a user preferences and gridding options interface 1106. Asdescribed above, the user preferences and gridding options interface1106 enables a user to specify various user preferences and griddingoptions, such as the inputs to the near-well unstructured grid modelbuilder 110. The gridding options may include, for example, the gridsize, the field rectangle polygon, and other options.

The graphical user interface 1102 also includes 2D and 3D renderingtools 1108 to render various data visually and display thevisualizations to the user. For example, as described above, the 2D and3D rendering tools 1108 may visualize the well trajectory and completiondata in both 2D and 3D and the field polygon. Moreover, visualizationsmay use user-selected colors to display different types of data.Additionally, as described above, the 2D and 3D rendering tools 1108 mayenable a user to zoom in and zoom out on various wells, jump todifferent wells, rotate and pan the camera, and provide other viewingcontrols. The graphical user interface 1102 also includes a drawing tool1110 that enables a user to define regions of interest of the field bydrawing a reservoir polygon. Such drawing functionality may beimplemented by enabling a user to define points of a polygon and connectthe points, using, for example, rubber-band selection.

As also mentioned above, the graphical user interface 1102 includes ajob interface 1112 that enables a user to submit and monitor computingjobs provided to a computing environment, such as an HPC cluster. Forexample, a user may submit parallel model building jobs for the parallelunstructured grid model builder 202 for execution by the computingenvironment. The job interface 1112 to queue jobs, view existing jobs,view job status, and so on.

The graphical user interface 1102 also includes a property analysis tool1114 and a perforation analysis tool 1116. As described above, afterbuilding an unstructured grid mode, the geometry, properties, and wellperforations of the unstructured grid may be viewed by a user in theworkflow interface 200 for verification. The generated unstructured gridgeometry may be displayed in the 2D and 3D rendering tools 1108, Forexample, the 2D rendering tool may display the generated Voronoi cellsand grid points. The property analysis tool 1114 may display theproperties of the generated unstructured grid by using, for example, acolor-mapping scheme to display the properties at each unstructured gridcell and at each geological grid level. The color mapping scheme may bea default scheme or a user-selected color mapping scheme. Additionally,the property analysis tool 1114 may provide a dropdown list or otheruser interface element for selection of individual properties.Additionally, the property analysis tool 1114 may visualize multiplegrid layers at the same time to enable viewing of property values acrossall grid layers.

As described above, the perforation analysis tool enables a user to viewperforation of all wells, groups of wells, or individual wells based onuser-selectable viewing options. The perforation analysis tool 1116displays the perforated cells in highlights (e.g., in a specific color)and may optionally display the exit-entry points of the well trajectory.Moreover, the perforation analysis tool 1116 may draw intersected cellsalong with the corresponding well peroration path in 2D and 3D, and mayalso show the intersection points on the cell.

The graphical user interface 1102 may also include a region dataconstructor 1118 for converting a first region format (e.g., astructured grid format) to a second region format (e.g. an unstructuredgrid format). As described above, in some embodiments, the region datain structured grid format may be converted to MODIFY region data as partof MODIFY statements used by a parallel reservoir simulator (e.g., theparallel reservoir simulator 112.). The region data constructor 1118 mayenable a user to select unstructured grid cells or regions directly fromthe unstructured grid and build the unstructured region data visually.The region data constructor 1118 may enable a user to select grid cellsvia rubber-band selection and then select a 3D layer range forconstruction of a 3D region for format conversion.

FIGS. 12 and 13 depict operation of the workflow interface 200 and theparallel unstructured grid model builder 202 in accordance with anembodiment of the present invention. FIGS. 12A and 12B depict a process1200 of the workflow interface 200, and FIGS. 13A and 13B depict aprocess 1300 of the parallel unstructured grid model builder. Withregard to the workflow interface 200, a user preferences and griddingoptions interface may be provided (block 1202). Next, input dataspecified by the user may be received (block 1204). As described, theinput data may include existing well trajectory and completion data,future well data (e.g., future well trajectory and completion data), astructured geological model, a structured grid simulation model, or anycombination thereof.

Next, gridding options may be received in the workflow interface (block1206). For example, as described above, a grid size and other griddingoptions may be specified by the user. Additionally, user preferences maybe received (block 1208). Such user preferences may include, forexample, customization of the graphical user interface implementing theworkflow interface, colors for various rendered visualizations providedin the workflow interface, and other user preferences. Next, the fieldpolygon is defined based on the input data (block 1210). For example,the field polygon may be based on some or all of the different types ofinput data provided via the workflow interface.

Next the visualized well trajectory and completion data are displayedfor review (block 1212). As mentioned above, in some embodiments, thewell trajectory and completion data are visualized in a 2D and 3Drendering tool that enables both 2D and 3D viewing of the data in thevisualization. Next, a reservoir polygon may be defined (block 1214)based on actions by the user. In the case of multiple reservoirs in thefield, multiple reservoir polygons may be defined. As described above,after viewing the field polygon, the user may create a reservoir polygonor multiple reservoir polygons, each may optionally contain one or moreregions of interest. Each region of interest may have a user-specifiedgrid size smaller than the reservoir grid size.

As shown by connection block A, FIG. 12B depicts further details of theprocess 1200. After defining a reservoir polygon, a job interface isprovided in the workflow interface (block 1216). As described above, thejob interface enables a user to submit jobs for the parallelunstructured grid model builder and monitor submitted jobs. Thus, jobsubmissions may be received (block 1218). As described above, the jobsubmissions are provided to the parallel unstructured grid model builderfor generation of a near-well unstructured grid.

FIG. 13A depicts a process 1300 of the parallel unstructured grid modelbuilder in accordance with an embodiment of the present invention. Asshown by connection block B from FIG. 13B, unstructured gridding datafor submitted jobs is received (block 1302). The gridding data andassociated gridding options (e.g., gridding options entered by a userand received in the workflow interface) are verified (block 1304). Next,the well trajectory and perforation data is analyzed (block 1306). Asdescribed above, the analysis may include determining compatibilitybetween well trajectory data and perforation data and sampling welltrajectory points contained by perforation start and end points.

Following the analysis, grid points in each region of interest aregenerated and optimized (block 1308). As described above, theoptimization may include weighting various grid points, replacing gridpoints, and placing grid points to provide an optimal grid layout forthe whole domain. Next, an unconstrained Delauney triangulation of thefield domain is performed using the generated grid points (block 1310).After the Delauney triangulation, a Voronoi grid (which may also bereferred to as a PEBI grid) having Voronoi cells is generated (block1312), such as via perpendicular bisection of the triangle edges of theDelauney triangulation. As illustrated by connection block B, theprocess 1300 is further depicted in FIG. 13B.

As shown by connection block B and as illustrated in FIG. 13B, theprocess 1300 then generates an unstructured grid geometry (block 1314),generates unstructured grid properties (block 1316), and generatesunstructured grid perforation (1318). After generating the geometry,properties, and perforation for the unstructured grid, the unstructuredgrid may be output (block 1320). As described above, the unstructuredgrid may then be provided to a parallel reservoir simulator for furtherprocessing (1322).

As described, generating unstructured grid geometry (block 1314) mayinclude generates the 2.5D unstructured grid geometry for the entiredomain. Additionally, as shown by connection block C, the unstructuredgrid geometry may be displayed by the workflow interface process. Withreference to FIG. 12B and as shown by connection block C, the workflowinterface process 1200 may display Voronoi cells and grid points in arendering tool (block 1220). For example, a user may use the renderingtool to examine the correlation between the Voronoi cells and thetriangulation grid points.

As mentioned above and as shown in FIG. 13B, the process 1300 includesgenerating unstructured grid properties (block 1316). As shown byconnection block D, the unstructured grid properties may be displayed bythe workflow interface process. As shown in FIG. 12B and by connectionblock D, the workflow interface process 1200 may display the generatedproperties in a property analysis tool (block 1222). As shown in FIG.13B and as mentioned above, the process 1300 includes generatingunstructured grid perforation (block 1318). As described above and asshown by connection block E in FIGS. 13B and 12B, the unstructured gridperforation may be displayed by the workflow interface process. As shownin FIG. 12B, the workflow interface process may display the generatedunstructured grid perforation in a perforation analysis tool (block1224).

Additionally, as described above, the workflow interface may include aregion data constructor. Thus, in some embodiments and as depicted inFIG. 12B, a region data constructor may be provided in the workflowinterface (block 1226). Selected grid cells or regions for formatconversion may be received (block 1228) and, in some embodiments,unstructured MODIFY region data may be constructed from the selectedgrid cells or regions (block 1230)

FIG. 14 depicts a process 1400 for using the near-well unstructured gridmodel builder in accordance with an embodiment of the present invention.Initially, a user may launch the near-well unstructured grid modelbuilder (block 1402). For example, after launch a user may be presentedwith a GUI providing the workflow interface. Next, the user may create aproject for the simulation and the near-well modeling (block 1404). Theuser may then populate the project with input data (block 1408). Asdescribed above, the input data may include existing well trajectoriesand completion data, future well data, a geological model, a structuredgrid simulation model, or any combination thereof.

The user may then define gridding options (block 1408), such as byspecifying the grid size. Additionally, as described above, a user maycreate a reservoir polygon within a field polygon to define regions ofinterest. Next, the user may submit parallel unstructured model buildingjobs to a computing environment (block 1410). For example, in someembodiments, the computing environment may include an HPC cluster andthe user may submit cluster jobs for execution by the HPC cluster. Aftergeneration of the unstructured grid, the user may review the generatedunstructured grid (block 1412). In some embodiments, as described above,the user may view the generated unstructured grid geometry, thegenerated unstructured grid properties, and the generated unstructuredgrid perforation in the workflow interface. For example, the user mayexamine the generated unstructured grid for the grid point density,quality of near-well region representation, smoothness of gridtransition, and so on. If the user is satisfied with the generatedunstructured grid, the user may export the grid to the parallelreservoir simulator (block 1414).

As shown by connection block F, the process 1400 is further illustratedin FIG. 14B. After a reservoir simulation is performed by the parallelreservoir simulator, the user may import the simulation results into theviewer and analyzer (block 1416). The user may then perform furthertasks based on additional data input into the process. For example, auser may predict future performance by importing recurrent data of anexisting simulation model or the coordinates of future wells (block1418). As shown by connection block H, the process may then continuewith the user defining gridding options and proceeding with additionalunstructured grid generation. Additionally, a user may perform historymatching by constructing region data (block 1420). For example, MODIFYregion data may be constructed for sensitivity analysis and simulationmodel updating using AHM (assisted history match) tool to match theproduction history. For an already history matched structured gridmodel, the matched data may be imported (block 1422) and, as shown byconnection block H, the process may continue with the user defininggridding options (block 1406). The structured grid MODIFY data may begenerated by the parallel unstructured grid model builder and may beconstructed using the workflow interface, as described above.

FIG. 15 depicts a system 1500 implementing a near-well unstructured gridmodel builder 1502 in accordance with an embodiment of the presentinvention. The system 1500 includes a client computer 1504, a network1506, a computing environment 1508, and a reservoir simulator 1510. Asshown in FIG. 15, the near-well unstructured grid model builder1502-includes a workflow interface 1512 and a parallel unstructured gridmodel builder 1514. The unstructured grid builder 1502 may produce anunstructured grid model 1516, according to the techniques describedabove. As described above, the unstructured grid model 1516 is providedto the reservoir simulator 1510, and the reservoir simulator 1510produces a reservoir simulation 1518 based on the unstructured grid. Itshould be appreciated that, in some embodiments, the reservoir simulator1510 may be implemented on a computing environment similar to thecomputing environment 1508.

A user may use the client computer 1504 to access the near-wellunstructured grid model builder 1502 over the network 1506. For example,as described above, the workflow interface 1512 may be implemented in agraphical user interface, and the client computer 1504 may be used toaccess and interact with the graphical user interface. The clientcomputer 1504 may include, for example, laptop computers, desktopcomputers, tablet computers, or other computers. In some embodiments,the network 1506 may include multiple networks, such as a wirelessEthernet network, a cellular network, or other wireless networks. Thecomputing environment 1508 may include single server (in a discretehardware component or as a virtual server) or multiple servers. Thecomputing environment 1508 may include web servers, application servers,or other types of servers. Additionally, the computing environment 1508may include, for example, computers arranged in any physical and virtualconfiguration, such as computers in one or more data processing centers,a distributed computing environment, an HPC cluster or otherconfiguration. Such configurations may use the network 1506 forcommunication or may communicate over other networks.

FIG. 16 depicts a computer 1600 in accordance with an embodiment of thepresent invention. Various sections of systems and methods describedherein may include or be executed on one or more computers similar tocomputer 1600 and programmed as special-purpose machines by executingsome or all steps of methods described above as executable computercode. Further, processes and modules described herein may be executed byone or more processing systems similar to that of computer 1600.

The computer 1600 may include various internal and external componentsthat contribute to the function of the device and which may allow thecomputer 1600 to function in accordance with the techniques discussedherein. As will be appreciated, various components of computer 1600 maybe provided as internal or integral components of the computer 1600 ormay be provided as external or connectable components. It should furtherbe noted that FIG. 16 depicts merely one example of a particularimplementation and is intended to illustrate the types of components andfunctionalities that may be present in computer 1600.

Computer 1600 may include any combination of devices or software thatmay perform or otherwise provide for the performance of the techniquesdescribed herein. For example, computer 1600 may include or be acombination of a cloud-computing system, a data center, a server rack orother server enclosure, a server, a virtual server, a desktop computer,a laptop computer, a tablet computer, a mobile telephone, a personaldigital assistant (PDA), a media player, a game console, avehicle-mounted computer, or the like. Computer 1600 may also beconnected to other devices that are not illustrated, or may operate as astand-alone system. In addition, the functionality provided by theillustrated components may in some embodiments be combined in fewercomponents or distributed in additional components. Similarly, in someembodiments, the functionality of some of the illustrated components maynot be provided or other additional functionality may be available.

In addition, the computer 1600 may allow a user to connect to andcommunicate through a network 1613 (e.g., the Internet, a local areanetwork, a wide area network, etc.) and may provide communication over asatellite-based positioning system (e.g., GPS). As shown in FIG. 16, thecomputer 1600 may include one or more processors (e.g., processors 1602a-1602 n) coupled to a memory 1604, a display 1606, I/O ports 1608 and anetwork interface 1610, via an interface 1614.

In one embodiment, the display 1606 may include a liquid crystal display(LCD) or an organic light emitting diode (OLED) display, although otherdisplay technologies may be used in other embodiments. The display 1606may display a user interface (e.g., a graphical user interface). Thedisplay 1606 may also display various function and system indicators toprovide feedback to a user. In accordance with some embodiments, thedisplay 1606 may include a “touch screen” and may also be known as orcalled a touch-sensitive display system.

The processor 1602 may provide the processing capability required toexecute the operating system, programs, user interface, and anyfunctions of the computer 1600. The processor 1602 may include one ormore processors, such general and special purpose microprocessors, suchas ASICs. For example, the processor 1602 may include one or morereduced instruction set (RISC) processors, such as those implementingthe Advanced RISC Machine (ARM) instruction set. Additionally, theprocessor 1602 may include single-core processors and multicoreprocessors and may include graphics processors, video processors, andrelated chip sets. A processor may receive instructions and data from amemory (e.g., system memory 1604). Accordingly, computer 1600 may be auni-processor system including one processor (e.g., processor 1602 a),or a multi-processor system including any number of suitable processors(e.g., 1602 a-1602 n). Multiple processors may be employed to providefor parallel or sequential execution of one or more sections of thetechniques described herein. Processes, such as logic flows, describedherein may be performed by one or more programmable processors executingone or more computer programs to perform functions by operating on inputdata and generating corresponding output.

The memory 1604 (which may include tangible non-transitory computerreadable storage mediums) may include volatile memory and non-volatilememory accessible by the processor 1602 and other components of thecomputer 1600. The memory 1604 may store a variety of information andmay be used for a variety of purposes. For example, the memory 1604 maystore application instructions, such as the firmware for the computer1600, an operating system for the computer 1600, and any other programsor executable code necessary for the computer 1600 to function. Programinstructions 1616 may be executable by a processor (e.g., one or more ofprocessors 1602 a-1602 n) to implement one or more embodiments of thepresent techniques. Instructions 1616 may include modules of computerprogram instructions for implementing one or more techniques describedherein with regard to various processing modules. Program instructionsmay include a computer program (which in certain forms is known as aprogram, software, software application, script, or code). A computerprogram may be written in a programming language, including compiled orinterpreted languages, or declarative or procedural languages. Acomputer program may include a unit suitable for use in a computingenvironment, including as a stand-alone program, a module, a component,a subroutine. A computer program may or may not correspond to a file ina file system. A program may be stored in a section of a file that holdsother programs or data (e.g., one or more scripts stored in a markuplanguage document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or sections of code). A computer programmay be deployed to be executed on one or more computer processorslocated locally at one site or distributed across multiple remote sitesand interconnected by a communication network. In addition, the memory1604 may be used for buffering or caching during operation of thecomputer 1600.

As mentioned above, the memory 1604 may include volatile memory, such asrandom access memory (RAM). The memory 1604 may also includenon-volatile memory, such as ROM, flash memory, a hard drive, any othersuitable optical, magnetic, or solid-state storage medium, or acombination thereof. The memory 1604 may store data files such as media(e.g., music and video files), software (e.g., for implementingfunctions on computer 1600), and any other suitable data. The interface1614 may include multiple interfaces and may couple various componentsof the computer 1600 to the processor 1602 and memory 1604. In someembodiments, the interface 1614, the processor 1602, memory 1604, andone or more other components of the computer 1600 may be implemented ona single chip, such as a system-on-a-chip (SOC). In other embodiments,these components, their functionalities, or both may be implemented onseparate chips. The interface 1614 may be configured to coordinate I/Otraffic between processors 1602 a-1602 n, system memory 1604, networkinterface 161160, I/O devices 1612, other peripheral devices, or acombination thereof. The interface 1614 may perform protocol, timing orother data transformations to convert data signals from one component(e.g., system memory 1604) into a format suitable for use by anothercomponent (e.g., processors 1602 a-1602 n). The interface 1614 mayinclude support for devices attached through various types of peripheralbuses, such as a variant of the Peripheral Component Interconnect (PCI)bus standard or the Universal Serial Bus (USB) standard.

The computer 1600 may also include an input and output port 1608 toallow connection of additional devices. Embodiments of the presentinvention may include any number of input and output ports 1608,including universal serial bus (USB) ports, Firewire or IEEE-1394 ports,and AC and DC power connectors. Further, the computer 1600 may use theinput and output ports to connect to and send or receive data with anyother device, such as other portable computers, personal computers,printers, etc. For example, in one embodiment the computer 1600 mayconnect to a personal computer via a USB connection to send and receivedata files, such as applications, media files, etc.

The computer 1600 depicted in FIG. 16 also includes a network interface1610, such as a wired network interface card (NIC), wireless (e.g.,radio frequency) receivers, etc. For example, the network interface 1610may receive and send electromagnetic signals and communicate withcommunications networks and other communications devices via theelectromagnetic signals. The network interface 1610 may include anantenna system, an RF transceiver, one or more amplifiers, a tuner, oneor more oscillators, a digital signal processor, a CODEC chipset, asubscriber identity module (SIM) card, memory, and so forth. The networkinterface 1610 may communicate with networks (e.g., network 1613), suchas the Internet, an intranet, a cellular telephone network, a wirelesslocal area network (LAN), a metropolitan area network (MAN), or otherdevices by wireless communication.

Those skilled in the art will also appreciate that, while various itemsare illustrated as being stored in memory or on storage while beingused, these items or sections of them may be transferred between memoryand other storage devices for purposes of memory management and dataintegrity. Alternatively, in other embodiments some or all of thesoftware components may execute in memory on another device andcommunicate with the illustrated computer system via inter-computercommunication. Some or all of the system components or data structuresmay also be stored (e.g., as instructions or structured data) on acomputer-accessible medium or a portable article to be read by anappropriate drive, various examples of which are described above. Insome embodiments, instructions stored on a computer-accessible mediumseparate from computer 1600 may be transmitted to computer 1600 viatransmission media or signals such as electrical, electromagnetic, ordigital signals, conveyed via a communication medium such as a networkor a wireless link. Various embodiments may further include receiving,sending or storing instructions or data implemented in accordance withthe foregoing description upon a computer-accessible medium.Accordingly, the present invention may be practiced with other computersystem configurations.

Various embodiments may further include receiving, sending or storinginstructions and/or data implemented in accordance with the foregoingdescription upon a computer-accessible medium. Generally speaking, acomputer-accessible/readable storage medium may include a non-transitorystorage media such as magnetic or optical media, (e.g., disk orDVD/CD-ROM), volatile or non-volatile media such as RAM (e.g. SDRAM,DDR, RDRAM, SRAM, etc.), ROM, etc., as well as transmission media orsignals such as electrical, electromagnetic, or digital signals,conveyed via a communication medium such as network and/or a wirelesslink.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as examples of embodiments. Elements and materials maybe substituted for those illustrated and described herein, parts andprocesses may be reversed or omitted, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims. Headings used herein are for organizational purposesonly and are not meant to be used to limit the scope of the description.

What is claimed is:
 1. A computer-implemented method for generating anear-well unstructured grid, the method comprising: receiving, by one ormore processors, input data, the input data comprising: a structuredgeocellular model having a well or a structured reservoir simulationmodel having a well; and well trajectory data and completion data forthe well; determining, by one or more processors, a field polygon basedon the input data; determining, by one or more processors, a reservoirpolygon having a region of interest containing the well; generating, byone or more processors, a plurality of grid points, the plurality ofgrid points comprising: a plurality of field grid points based on auser-specified field grid size; and a plurality of reservoir grid pointsbased on a user-specified reservoir grid size for each reservoir; aplurality of well grid points based on a well grid size; and a pluralityof parallel near-wellbore grid points on both sides of each of theplurality of well grid points based on the well grid size; performingconflicting point removal and point adjustments to generate a pluralityof final grid points based on a point prioritization of weights assignedto the plurality of grid points; performing, by one or more processors,a Delaunay triangulation based on the plurality of final grid points;generating, by one or more processors, a Voronoi grid based on theDelaunay triangulation; generating, by one or more processors, anear-well unstructured grid based on the Voronoi grid, the generatingcomprising: generating a geometry of the near-well unstructured grid;generating properties of the near-well unstructured grid; and generatingperforation of the near-well unstructured grid; and providing, by one ormore processors, the near-well unstructured grid to a parallel reservoirsimulator.
 2. The method of claim 1, comprising performing a reservoirsimulation of the near-well unstructured grid via the parallel reservoirsimulator.
 3. The method of claim 1, wherein the plurality of gridpoints comprises a plurality of region of interest grid points based ona user-specified region of interest grid size for the region ofinterest.
 4. The method of claim 1, wherein generating the plurality ofgrid points comprises a plurality of multi-level quad-tree local gridrefinement (LGR) grid points based on a user-specified number of levelsand user specified near-well distances.
 5. The method of claim 1,wherein generating the geometry of the near-well unstructured gridcomprises generating a 2.5D unstructured grid geometry.
 6. The method ofclaim 5, wherein generating the geometry of the near-well unstructuredgrid comprises computing a depth to a bounding surface of each gridlayer.
 7. The method of claim 5, wherein the generated unstructured gridgeometry comprises a layer geometry of the structured geocellular modelor a structured reservoir simulation model.
 8. The method of claim 1,wherein generating properties of the near-well unstructured gridcomprising applying interpolation or point injection from a propertyvalue of the structured geocellular model or a structured reservoirsimulation model to a grid point center of the near-well unstructuredgrid, such that the unstructured grid property maps closely match theoriginal structured grid property maps.
 9. The method of claim 1,wherein generating a perforation of the near-well unstructured gridcomprising computing an intersection point of the well trajectory andwell completion data with a finite volume cell face of one or more ofthe plurality of grid cells penetrated by a wellbore of the well. 10.The method of claim 1, comprising providing a graphical user interfaceto a user, the graphical user interface comprising an interface forspecifying the input data.
 11. The method of claim 1, wherein thegraphical user interface comprises a rendering tool for visualizing thegenerated unstructured grid geometry.
 12. The method of claim 1, whereinthe graphic graphical user interface comprises a property analysis toolfor displaying the generated unstructured grid properties.
 13. Themethod of claim 1, wherein the graphical user interface comprises aperforation analysis tool for displaying the generated unstructured gridperforation.
 14. A non-transitory tangible computer-readable storagemedium having executable computer code stored thereon, the computer codecomprising a set of instructions that causes one or more processors toperform the following: receiving, by one or more processors, input data,the input data comprising: a structured geocellular model or astructured reservoir simulation model having a well; and well trajectorydata and completion data for the well; determining, by one or moreprocessors, a field polygon based on the input data; determining, by oneor more processors, a reservoir polygon having a region of interestcontaining the well; generating, by one or more processors, a pluralityof grid points, the plurality of grid points comprising: a plurality offield grid points based on a user-specified field grid size; a pluralityof reservoir grid points based on a user-specified reservoir grid sizefor each reservoir; a plurality of well grid points based on a well gridsize; and a plurality of parallel near-wellbore grid points on bothsides of each of the plurality of well grid points based on the wellgrid size; performing conflicting point removal and point adjustments toproduce a plurality of final grid points based on a point prioritizationof weights assigned to the plurality of grid points; performing, by oneor more processors, a Delaunay triangulation based on the plurality offinal grid points: generating, by one or more processors, a Voronoi gridbased on the Delaunay triangulation; generating, by one or moreprocessors, a near-well unstructured grid model based on the Voronoigrid, the generating comprising: generating a geometry of the near-wellunstructured grid model; generating properties of the near-wellunstructured grid model; and generating perforation of the near-wellunstructured grid model; and providing, by one or more processors, thenear-well unstructured grid to a parallel reservoir simulator.
 15. Thenon-transitory tangible computer-readable storage medium of claim 14,the computer code further comprising a set of instructions that causesone or more processors to perform the following: performing a reservoirsimulation of the near-well unstructured grid via the parallel reservoirsimulator.
 16. The non-transitory tangible computer-readable storagemedium of claim 14, wherein plurality of grid points comprises aplurality of region of interest grid points based on a user-specifiedregion of interest grid size for the region of interest.
 17. Thenon-transitory tangible computer-readable storage medium of claim 14,wherein the plurality of grid points comprises a plurality ofmulti-level quad-tree local grid refinement (LGR) grid points based on auser-specified number of levels and user specified near-well distances.18. The non-transitory tangible computer-readable storage medium ofclaim 14, wherein generating the geometry of the near-well unstructuredgrid comprises generating a 2.5D unstructured grid geometry.
 19. Thenon-transitory tangible computer-readable storage medium of claim 18,wherein generating the geometry of the near-well unstructured gridcomprises computing a depth to a bounding surface of each grid layer.20. The non-transitory tangible computer-readable storage medium ofclaim 18, wherein the generated unstructured grid geometry comprises alayer geometry of the structured geocellular model or a structuredreservoir simulation model.
 21. The non-transitory tangiblecomputer-readable storage medium of claim 14, wherein generatingproperties of the near-well unstructured grid comprising applying aninterpolation or point injection from a property value of the structuredgeocellular model or a structured reservoir simulation model to a gridpoint center of the near-well unstructured grid, such that theunstructured grid property maps closely match the original structuredgrid property maps.
 22. The non-transitory tangible computer-readablestorage medium of claim 14, wherein generating a perforation of thenear-well unstructured grid comprising computing an intersection pointof the well trajectory data with a finite volume cell face of one ormore of the plurality of grid cells penetrated by a wellbore of thewell.
 23. The non-transitory tangible computer-readable storage mediumof claim 14, the computer code further comprising a set of instructionsthat causes one or more processors to perform the following: providing agraphical user interface to a user, the graphical user interfacecomprising an interface for specifying the input data.
 24. Thenon-transitory tangible computer-readable storage medium of claim 14,wherein the graphical user interface comprises a rendering tool forvisualizing the generated unstructured grid geometry.
 25. Thenon-transitory tangible computer-readable storage medium of claim 14,wherein the graphic graphical user interface comprises a propertyanalysis tool for displaying the generated unstructured grid properties.26. The non-transitory tangible computer-readable storage medium ofclaim 14, wherein the graphical user interface comprises a perforationanalysis tool for displaying the generated unstructured gridperforation.
 27. A system, comprising: one or more processors; anon-transitory tangible computer-readable memory having executablecomputer code stored thereon, the computer code comprising a set ofinstructions that causes one or more processors to perform thefollowing: receiving, by the one or more processors, input data, theinput data comprising: a structured geocellular model having a well or astructured reservoir simulation model having a well; and well trajectorydata and completion data for the well; and determining, by the one ormore processors, a reservoir polygon having a region of interestcontaining the well; generating, by one or more processors, a pluralityof grid points, the plurality of grid points comprising: a plurality offield grid points based on a user-specified field grid size; a pluralityof reservoir grid points based on a user-specified reservoir grid sizefor each reservoir; a plurality of well grid points based on a well gridsize; and a plurality of parallel near-wellbore grid points on bothsides of each of the plurality of well grid points based on the wellgrid size; performing conflicting point removal and point adjustments toproduce a plurality of final grid points based on a point prioritizationof weights assigned to the plurality of grid points; performing, by theone or more processors, a Delaunay triangulation based on the pluralityof final grid points: generating, by the one or more processors, aVoronoi grid based on the Delaunay triangulation; generating, by the oneor more processors, a near-well unstructured grid based on the Voronoigrid, the generating comprising: generating a geometry of the near-wellunstructured grid; generating properties of the near-well unstructuredgrid; and generating a perforation of the near-well unstructured grid;and providing, over a network coupled to the one or more processors, thenear-well unstructured grid to a parallel reservoir simulator.
 28. Thesystem of claim 27, the computer code further comprising a set ofinstructions that causes one or more processors to perform thefollowing: performing a reservoir simulation of the near-wellunstructured grid via the parallel reservoir simulator.
 29. The systemof claim 27, wherein the plurality of grid points comprises a pluralityof multi-level quad-tree local grid refinement (LGR) grid points basedon a user-specified number of levels and user specified near-welldistances.
 30. The system of claim 27, wherein generating the geometryof the near-well unstructured grid comprises generating a 2.5Dunstructured grid geometry.
 31. The system of claim 30, whereingenerating the geometry of the near-well unstructured grid comprisescomputing a depth to a bounding surface of each grid layer.
 32. Thesystem of claim 27, comprising a client computer coupled to the one ormore processors, the client computer configured to provide a graphicaluser interface to a user, the graphical user interface comprising aninterface for specifying the input data.
 33. The system of claim 27,wherein the graphical user interface comprises a rendering tool forvisualizing the generated unstructured grid geometry.
 34. The system ofclaim 27, wherein the graphic graphical user interface comprises aproperty analysis tool for displaying the generated unstructured gridproperties.
 35. The system of claim 27, wherein the graphical userinterface comprises a perforation analysis tool for displaying thegenerated unstructured grid perforation.
 36. A non-transitory tangiblecomputer-readable storage medium having executable computer code storedthereon for a workflow interface for generating a near-well unstructuredgrid, the computer code comprising a set of instructions that causes oneor more processors to perform the following: define a workflow interfacefor a near-well unstructured grid builder, the workflow interfaceconfigured to: define input data for the near-well unstructured gridbuilder; define gridding options for the near-well unstructured gridbuilder; display well data of the input data in a 2D or 3Dvisualization; provide well data and a region of interest within theinput data to an unstructured grid model builder for generation of anunstructured grid; display geometry of the generated unstructured grid;display the properties of the generated unstructured grid; and displaythe perforation of the generated unstructured grid.
 37. Thenon-transitory tangible computer-readable storage medium of claim 36,the workflow interface comprising a graphical user interface.
 38. Thenon-transitory tangible computer-readable storage medium of claim 36,the workflow interface configured to well data of the input data in a 2Dor 3D visualization according to user-selected colors.
 39. Thenon-transitory tangible computer-readable storage medium of claim 36,the workflow interface configured to well data of the input data in a 2Dor 3D visualization according to user-selected colors.
 40. Acomputer-implemented method for constructing an unstructured grid,comprising: receiving, by one or more processors, a structured gridhaving a first plurality of grid points and a well of a reservoir;determining, by one or more processors, a region of interest in thestructured grid; generating, by one or more processors, a secondplurality of grid points in the region of interest according to a firstgrid size: generating, by one or more processors, a third plurality ofgrid points outside of the region of interest according to a second gridsize; constructing, by one or more processors, a 2.5D unstructured gridfrom the second plurality of grid points and the third plurality of gridpoints; and processing, by one or more processors, the 2.5 unstructuredgrid via a reservoir simulator to produce a simulation of the reservoir.41. The method of claim 40, comprising generating, by one or moreprocessor, properties of the 2.5D unstructured grid based on propertiesof the structured grid.
 42. The method of claim 40, comprisingreceiving, by one or more processors, well trajectory data andcompletion data for the well.
 43. The method of claim 40, wherein the2.5D unstructured grid comprises a reservoir layer geometry of thestructured grid.